Heretofore, there has been well known such an egg yolk phospholipid composition that is obtained by breaking an egg, separating egg yolk from the broken egg, drying the egg yolk to obtain dried egg yolk, allowing, for instance, an alcohol to act on the dried egg yolk to extract alcohol-soluble components therefrom, and then removing the alcohol from the extract. The egg yolk phospholipid composition obtained in this manner generally contains at least 20% of egg yolk phospholipids. A purification process required for producing a crude product whose phospholipids content is 80% or less is not so complicated and difficult as that required for producing a product whose phospholipids content is higher than 80%, so that such a crude product can be obtained at relatively low cost. Therefore, the crude product has been made into a capsule preparation by being placed in capsules made from, for example, gelatin, and hitherto widely used as, for instance, a complementary food for health, an enriched food for the brain, or the like.
However, the above capsule preparation has had such a problem that, when it is placed in a bottle and the bottle is capped air-tightly and stored, for instance, at a normal temperature, the color of the capsule preparation changes from bright yellow to dark brown within approximately 3 months, and its appearance is thus drastically impaired. It seems that this change in color occurs because the egg yolk phospholipid composition contained in the capsules undergoes such a reaction as oxidation or polymerization. It is noted that the above problem has rarely been found in a capsule preparation obtained by using a phospholipid composition whose phospholipids content is higher than 80%, that is, a phospholipid composition which has been purified so that it will have, as phospholipids, a purity of higher than 80%.
A primary object of the present invention is therefore to provide a novel egg yolk phospholipid composition whose color scarcely changes to brown during the preservation thereof although the phospholipids purity of the composition is not so high, that is, the phospholipids content of the composition is only 80% or less.